Mike is well known. He's one of the most successful angel investors in tech, having taken an early stake in Twitter, Digg, and other successful startups.

But who is Ann Miura-Ko? Partnering with Mike makes her one of the most powerful angel investors in the Valley. That makes her one of the most powerful women in tech.

We figured we should all know a little more about her. So we called Mike, Ann, and some of our sources in angel investing.

Here's what we learned:

On her LinkedIn profile, she describes herself as an "investing ninja assassin."

She majored in electrical engineering at Yale. After college, she spent three years at McKinsey, launching wireless Internet companies in the US and abroad.

She spent two years at Charles River Ventures and then moved to Palo Alto for a Ph.D. program at Stanford. Now she teaches there.

The gig is great for getting leads on startups. She's had over 500 students pitch about 150 startup ideas to her.

Ann came to Maples Investments after a successful two year stint with Charles River Ventures.

Her first big hit at Maples came when she sourced its investment in ModCloth, an unlikely sounding Pittsburgh retailer of "vintage-inspired" clothing. The company reportedly took in $15 million in revenue last year.

On paper, Ann is just becoming a full time partner with this announcement. But she has essentially been in that role for some time now. Mike says it's a case of someone "being promoted into a job they're already doing."

Floodgate is a full and equal partnership between the two investors, but Ann still has a final hurdle to clear before she can be described as 100% full time at the new fund -- she is about to submit her dissertation to complete her PhD in quantitative modeling of computer security at Stanford.

Even after she's done with that, she will continue to teach entrepreneurship classes at Stanford. But that is a huge boost to Floodgate, rather than a distraction from it. Many successful startups are launched by Stanford students, and the hundreds of business plans she has evaluated as a teacher give her what Mike calls "proprietary access" to the best entrepreneurial talent coming out of the university.

Mike recognizes that Ann is one of the very few women in powerful positions in angel investing -- in tech, even -- and he says, "The industry's loss is my gain. In no way did I hire her because she's a woman, but there's definitely an advantage there. "

Given her academic background, it's not surprising that 100% of the people we talked to used the word "technical" in describing her strengths as an investor.

Mike says he's good at seeing the marketing and sales potential of the companies in which he invests, but Ann can understand the technical details of what a startup is up to in a way that most investors can't.

In the immediate future, the new arrangement won't have much of an impact on how the two do business. They plan to invest in the same sorts of companies and use the same strategy.

They probably won't raise money for a new fund until late 2010. But now that Ann's status is official, expect to see her joining the boards of more of the companies Floodgate invests in.

Here's a 2-minute clip about Ann from from TechCrunch's 20 minute interview with Floodgate: